Commentary to “linear and nonlinear system approaches in pharmacokinetics. How much do they have to offer? I. General considerations”

Summary The review by Veng-Pedersen will hopefully stimulate workers in the field to consider systems techniques more thoroughly. As these techniques are well developed in the engineering fields, students should be encouraged to take relevant courses. In this reviewer's opinion, understanding systems theory will allow pharmacokineticists to cut through the fat in the derivation of relationships between kinetic phenomena. However, it should be recognized that the system approaches described in Veng-Pedersen's review probably do not by themselves solve the major problems of response approximation and prediction.SeeJ. Pharmacokin, Biopharm. 16:413–472.     

Stability of chronic medicines in dosage administration aids. How much have been done?

Background

The prevalence of chronic diseases is increasing in Asia, therefore compliance to the medications is of utmost importance to slow disease progression and improve outcomes. Dosage administration aids (DAAs) serve as important tool to improve the compliance of patients. However, there is a dearth of data on the stability of chronic medications in DAAs. Furthermore, data presented by our Western counterparts may not be applicable to us because of our extreme humidity and temperature. In this study, we aim to summarize the data available in the literature on the stability of chronic medications in DAA.

Methods

We performed a literature search using electronic databases and related keywords.

Results

In total, 24,336 articles were retrieved and 21 articles were found to be relevant to our topic. This commentary stratified drugs according to their treatment categories and key stability conclusions, DAA and conditions used and recommendations were presented.

Conclusion

Due to the lack of specific data, pharmacists have to exercise their professional judgment with the help from professional guidelines when using DAA in repackaging medication. Manufacturers and regulators can play a greater role in filling the gap needed to provide pharmacists with necessary information to fulfill their function.     

Omega-3 fatty acids and HDL. How do they work in the prevention of cardiovascular disease?

Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) from marine origin have been strongly associated with cardiovascular protection, even at low doses ( < 1g/d). Despite the research performed in this promising area, basic aspects, such as the ideal doses and the mechanisms by which ω-3 PUFAs act, are not precisely defined. The best known biological property of ω-3 PUFAs is their hypotriglyceridemic effect, but other cardioprotective actions, such as reduction of arrhythmia susceptibility, antithrombotic, antiinflammatory and antioxidant effects, improvement of endothelial function, and delayed atherosclerosis development have received an increased interest in recent years. Some of these actions are also ascribable to high-density lipoproteins (HDL). Abundant epidemiological evidence links increasing HDL-cholesterol concentrations to cardiovascular protection. Recently, the protein cargo (proteome) of HDL particles has been attributed a key role in their functionality. In this review, we summarize the main effects of ω-3 PUFAs on HDL-cholesterol, HDL subfractions, and its main proteins, apolipoproteins (apo) AI and AII. The shared cardioprotective actions of ω-3 PUFAs and HDL are reviewed as well.     

How much do the public sector and the private sector contribute to biopharmaceutical R&D?

When examining the prices of new medicines, the question of how much the private and public sectors have contributed to their R&D is often raised. Contributions can be assessed in terms of the investment, authorship of publications, marketing authorizations and intellectual property rights associated with biopharmaceutical R&D. This review of the empirical evidence underlines the complementary and interwoven nature of the private and public sectors in supporting biopharmaceutical R&D. Both sectors invest in and contribute to biopharmaceutical R&D, with the public sector predominantly focusing on basic research and the private sector mainly targeting medicine discovery and development. Public-sector investment generates additional private-sector investment.     

How to enhance public health service utilization in community pharmacy?: General public and health providers' perspectives

BackgroundCommunity pharmacists (PHs) in England are increasingly providing a range of public health services. However, the general public view pharmacists as drug experts and not experts in health, and therefore, services may be underutilized.ObjectivesTo explore experiences and views of 4 groups of participants, the general public, PHs, general practitioners (GPs), and other stakeholders (STs) on pharmacy-based public health services, and identify potential factors affecting service use.MethodsThe study was undertaken in a locality of North West England. Three focus groups were conducted with the general public (n = 16), grouped by socioeconomic status. Fourteen semistructured interviews were undertaken with PHs (n = 9), GPs (n = 2), and STs (n = 3). Discussions/interviews were audio recorded, transcribed verbatim, and analyzed thematically.ResultsAll 4 groups of participants agreed that community pharmacies are a good source of advice on medicines and minor ailments but were less supportive of public health services. Six factors were identified affecting utilization of pharmacy services: community pharmacy environment, pharmacist and support staff, service publicity, general public, GP services, and health care system and policies. Crucial obstacles that could inhibit service utilization are perceptions of both the general public and other health providers toward pharmacists' competencies, privacy and confidentiality in pharmacies, high dispensing workload, and inadequate financial support. Networking between local health professionals could enhance confidence in service delivery, general awareness, and thus utilization.ConclusionsCommunity pharmacy has the potential to deliver public health services, although the impact on public health may be limited. Addressing the factors identified could help to increase utilization and impact of pharmacy public health services.     

Potassium channel openers and improvement of toxic stress: do they have role in the management of inflammatory bowel disease?

Inflammatory bowel disease (IBD) is a progressive condition in gastrointestinal tract, which refers to two idiopathic diseases; ulcerative colitis and Crohn's disease. Although certain etiology of these conditions is not known, it seems that an abnormality in reaction and regulation of the immune system plays an important role in adventure of the disease. According to the investigations, it is likely that oxidative and nitrosative stress have etiologic roles in IBD. Their destructive effects may contribute to the initiation or progression of the disease. Nowadays, the effectiveness of different medicines in the treatment of IBD has been proved, but none of them has shown a desirable result. Potassium channel openers (PCOs) are a class of drugs with various usages in the aspects of cardiovascular diseases and urinary incontinence. Their major mechanism is the opening of ATP-sensitive potassium (K-ATP) channels and contribute to the relaxation of smooth muscles. Nicorandil is a member of PCOs, with a special chemical structure. Recent investigations mention some novel effects and functions for this drug. Nicorandil reveals an anti-apoptosis property not only via a nitric oxide (NO)/cGMP-dependent mechanism, but also through activating mitochondrial K-ATP channels. Nicorandil can also elevate cGMP levels in some tissues, without direct NO generation. Gastroprotective activity via opening of the K channels, free radical scavenging, prostaglandin E2 elevation, decreasing pepsin and acid secretion, and prevention of the detrimental rise in NO has been proposed for nicorandil. According to these protective mechanisms and the role of oxidative/nitrosative stress in the expression of IBD, we herein hypothesize that nicorandil and other PCOs with similar structure can be used in the management of IBD. This approach offers new hope for the successful treatment of IBD. Further investigations on animal models are needed, to place nicorandil and similar drugs alongside IBD therapy.     

How much gets there and what does it do?: The need for better pharmacokinetic and pharmacodynamic endpoints in contemporary drug discovery and development

Drug discovery is an expensive, slow and high risk enterprise. Only one in ten of the agents that enter clinical development is successful, with an average cost of US dollars 500-800 million and a typical time-scale of 10-15 years from preclinical discovery research to regulatory approval. On the other hand, many new targets are emerging from genome sequencing and the improved understanding of molecular pathology. Also, new technologies are increasing the speed and improving the efficiency of drug discovery. These new advances should facilitate progress towards the development of personalised therapies that are targeted to the genetics and molecular pathology of individual patients. The availability of pharmacokinetic (PK) and pharmacodynamic (PD) endpoints is absolutely critical to modern drug development. They allow us to understand how much of the drug gets there (into the body and ideally to the target cells) and what it does (with respect to modulation of the molecular target and the cognate biochemical pathways and downstream biological effects). PK and PD endpoints allow us to construct a pharmacological audit trail, so that all of the successive stages from drug administration through to biological effects and clinical outcome can be monitored and interpreted. This in turn provides a rational basis for decision making, e.g. stop/go, during development. An understanding of PK/PD relationships also gives us s basis for selecting the optimal drug dose and schedule. Better, less invasive methods are required. Developments in molecular/functional imaging show promise and current examples are provided.     

Conformationally constrained analogues of diacylglycerol (DAG). 16. How much structural complexity is necessary for recognition and high binding affinity to protein kinase C?

The design of potent protein kinase C (PK-C) ligands with low nanomolar binding affinities was accomplished by the combined use of pharmacophore- and receptor-guided approaches based on the structure of the physiological enzyme activator, diacylglycerol (DAG). Earlier use of the former approach, which was based on the structural equivalence of DAG and phorbol ester pharmacophores, identified a fixed template for the construction of a semirigid "recognition domain" that contained the three principal pharmacophores of DAG constrained into a lactone ring (DAG-lactones). In the present work, the pharmacophore-guided approach was refined to a higher level based on the X-ray structure of the C1b domain of PK-Cdelta complexed with phorbol-13-O-acetate. A systematic search that involved modifying the DAG-lactone template with a combination of linear or branched acyl and alpha-alkylidene chains, which functioned as variable hydrophobic "affinity domains", helped identify compounds that optimized hydrophobic contacts with a group of conserved hydrophobic amino acids located on the top half of the C1 domain where the phorbol binds. The hydrophilic/hydrophobic balance of the molecules was estimated by the octanol/water partition coefficients (log P) calculated according to a fragment-based approach. The presence of branched alpha-alkylidene or acyl chains was of critical importance to reach low nanomolar binding affinities for PK-C. These branched chains appear to facilitate important van der Waals contacts with hydrophobic segments of the protein and help promote the activation of PK-C through critical membrane interactions. Molecular modeling of these DAG-lactones into an empty C1b domain using the program AutoDock 2.4 suggests the existence of competing binding modes (sn-1 and sn-2) depending on which carbonyl is directly involved in binding to the protein. Inhibition of epidermal growth factor (EGF) binding, an indirect PK-C mediated response, was realized with some DAG-lactones at a dose 10-fold higher than with the standard phorbol-12, 13-dibutyrate (PDBU). Through the National Cancer Institute (NCI) 60-cell line in vitro screen, DAG-lactone 31 was identified as a very selective and potent antitumor agent. The NCI's computerized, pattern-recognition program COMPARE, which analyzes the degree of similarity of mean-graph profiles produced by the screen, corroborated our principles of drug design by matching the profile of compound 31 with that of the non-tumor-promoting antitumor phorbol ester, prostratin. The structural simplicity and the degree of potency achieved with some of the DAG-lactones described here should dispel the myth that chemical complexity and pharmacological activity go hand in hand. Even as a racemate, DAG-lactone 31 showed low namomolar binding affinity for PK-C and displayed selective antitumor activity at equivalent nanomolar levels. Our present approach should facilitate the generation of multiple libraries of structurally similar DAG-lactones to help exploit molecular diversity for PK-C and other high-affinity receptors for DAG and the phorbol esters. The success of this work suggests that substantially simpler, high-affinity structures could be identified to function as surrogates of other complex natural products.     

Population Pharmacokinetic Modeling to Describe the Total Plasma and Free Brain Levels of Fluconazole in Healthy and <Emphasis Type="BoldItalic">Cryptococcus neoformans</Emphasis> Infected Rats: How Does the Infection Impact the Drug’s Levels on Biophase?

Purpose

The present work aimed to evaluate the influence of experimental meningitis caused by C. neoformans on total plasma and free brain concentrations of fluconazole (FLC) in Wistar rats.

Method

The infection was induced by the administration of 100 μL of inoculum (1.10⁵ CFU) through the tail vein. Free drug in the brain was assessed by microdialisys (μD). Blood and μD samples were collected at pre-determined time points up to 12 h after intravenous administration of FLC (20 mg/kg) to healthy and infected rats. The concentration-time profiles were analyzed by non-compartmental and population pharmacokinetics approaches.

Results

A two-compartmental popPK model was able to simultaneously describe plasma and free drug concentrations in the brain for both groups investigated. Analysis of plasma and μD samples showed a better FLC distribution on the brain of infected than healthy animals (1.04?±?0.31 vs 0.69?±?0.14, respectively). The probability of target attainment was calculated by Monte Carlo simulations based on the developed popPK model for 125 mg/kg dose for rats and 400–2000 mg for humans.

Conclusions

FLC showed a limited use in monotherapy to the treatment of criptoccocosis in rats and humans to value of MIC >8 μg/mL.